Heretofore can tops, or can end closures, have been made from metal discs cut from coil stock and then individually carried through a progressive die by a transfer mechanism which in regular order moves the separate discs from station to station for the necessary forming operations. This not only requires expensive and complicated apparatus for handling the individual pieces but is also slow in its output of finished can tops and often wasteful of the material from which the can tops are made.
A step in the direction of improving the manufacturing process for producing can tops is described in U.S. Pat. No. 3,888,199 which discloses a method for making a "press tab" or "button down" type of container end from a metallic web wherein the preliminary steps of forming and lancing the tabs or buttons are performed on the web at uniformly spaced areas comprising a predetermined web layout for batches of can ends. With the method of this patent, however, the preformed areas are then blanked-out of the web to provide individual can end discs or panels which are thereafter worked individually to produce the finished can ends, for example, in the manner described in U.S. Pat. No. 3,886,881.
The object of the present invention is to further simplify and improve the process of manufacturing easy open can tops, or can end closures, by doing all of the necessary lancing, panel forming, countersinking and embossing steps, except edge curling, while the can top blanks remain as integral parts of the metallic web, which is supplied as coil stock to a progressive die system, and then to do the edge curling by tools embodied in the same progressive die while in the same press.